1. Field of the Invention
The present invention is directed to circuitry structured to control the supply voltage to electric lighting systems of the type incorporating discharge lamps, hereinafter referred to as “discharge bulbs”, “discharge lamps” and/or “bulbs”.
2. Description of the Related Art
The use of discharge bulbs is increasingly popular for a variety of applications in the lighting or illumination industry. Such increased acceptance and utilization is due, at least in part, to economical reasons. Minimum power consumption per lumen compares favorably as compared to lighting or illuminating systems utilizing other lighting elements such as, but not limited to, incandescent and gas lamps.
However, it has long been known that inherent economic and operational disadvantages, resulting in the waste of electrical energy in many circuit structures and/or designs associated with conventional illumination systems, are due to the believed necessity of inductive loads. Such inductive loads play a role during the ignition and operational phases of the bulb or lighting element. Moreover, such operational or performance characteristics have no functional benefit other than limiting or restricting electrical current. Therefore, the presence of an inductance in the manner herein described comprises a constant ohmic and inductive resistance, causing energy loss through heat dissipation. Also, the amount of energy wasted is directly proportional to the current value flowing therethrough.
In order to gain a better understanding and appreciation of the problems and disadvantages associated with conventional illumination system circuitry of the type described, as well as a proposed solution, an examination of a prevalent and/or conventional single phase bulb, lighting circuit, is schematically represented in the prior art circuit of FIG. 1. As shown, the prior art system comprises the primary supply voltage VPN powering the lighting circuit which also includes bulb B, inductance L and capacitor C. The capacitor C is included for adjusting the power factor of the ignition circuit.
Assuming that the bulb B is of a conventional type, such as a 150 W General Electric® Sodium high pressure bulb, it is known that the rated operating voltage thereof is 113V. However, the rated primary voltage is 230V. Obviously, the voltage drop over inductance L must be 230VAC−113VAC=200VAC. It can therefore be shown that the impedance of the inductance L is calculated and designed so that the current through the bulb B, under the above conditions, is 0.88 A. However, tests have proven that the bulb B will continue to properly function (not become extinguished) even when the voltage drop there across is lowered to 109V. Such a reduced operating voltage results in a reduction in operating current of 0.62 A, while using the same inductance L.
The following table summarizes the results of tests conducted with the 150W GE® Sodium bulb:
TABLE 1VPN (v)VL (v)Ia(A)230113.88225113.35220113.83215113.81210112.76205111.72200110.67195109.62
The total consumption of the bulb B at a full supply voltage is 230×0.88=202 VA, and total energy consumption at the reduced voltage is 195×121 VA.
Hence, it is apparent that by reducing the input voltage by 230−195=35V (or 15%) the voltage drop on the inductance L is reduced from 200 VAC to 140 VAC, or by about 30%. Accordingly, the key for reducing the dissipated energy loss may be found in the non-linear relationship between the input voltage and the current flow through the bulb.
Various attempts have been made to accomplish the reduction of the main voltage to a minimum acceptable level without derogatorily affecting the bulb, such as by extinguishing the bulb after ignition or starting of the ionization process. However, none of the known or conventional attempts have proved to be successful, for a variety of reasons. By way of example, one such attempt incorporates the use of variac rheostats, tap changer transformers, inverters, and other devices. Such attempts are generally considered to be less than satisfactory because of, among other reasons, the step-like nature of the process and the fact that such devices are bulky, expensive and less than operationally reliable, demanding relatively frequent maintenance.
Accordingly one broad object of the present invention is to provide a method of and devices for controlling the input voltage supply of bulb lighting circuits that will effectively overcome the deficiencies of known or conventional circuitry.
It is a further object of the invention to provide a transformer-based switching system that will achieve the reduction of the input voltage in an effective manner.
It is a still further object of the invention that a switching system, as proposed herein, be readily operable by remote and/or possibly computerized means.